Beam amplifier tube



Sept. 2, 1952 N. z. BALLANTYNE BEAM AMPLIFIER TUBE Fil ed Feb. 15, 1950 INVENTOR ATTORNEYS.

Patented Sept. 2, 1952 i BEAM AMPLIFIER TUBE Ir.) a

Norman Z. Ballantyne, Lewiston, Idaho I 7 Application February 15, 1950, SerialNo. 144,223

' Claims. (01. 313-72) This invention f relates to improvements in electron tubes of thebeam. ainplifiert'ype'.

It is an object of the invention tofprovidea tube of 'thebeam amplifier t pe which willjen able direct coupling fromfthe' anodeiof'pfec'edin'gitube' to "its' controlling eleifient and thus provide a direct path for the signal voltagedef veloped across a plate load common to bothjlthe controlling element and theianodefwithoutithe use of cumbersome biasing "and divider circuits as has heretofore'b'een'necessary. j A further object is to providea tube which can be easily usedas'a direct current 'amp liiier. Her'etoiore, intubes the"control"element{had to 'be biased .below'or at .the' cathode potential requiri'ng cumbersome "circuits used without coupling. With the tube herein presented such circuits are not necessary as one control ele-- ment is always maintained positive with regard to the cathode, andincreasing it pofsitive merely increases the"electrostatic' lens action; and swinging it negative decreases-thelens ac ion;

"A further object is to provide a tube by means of which phase inversion is accomplishedi In the tube one element under controlwillaltt nately increase and decrease-the current flowing to each of two electrodeswhichhave-equal. opposite changes in current. Phase inversion can be accomplished bythe tube itself with the opposite phase removed from the equal plate loads of a target anodea'ndtarget-plate.- i I A further object is-to provide a tu be 'with a much more linear curve than possible -with 'tubes heretofore produced; and to provide-a: tube with high internal resistance) Also" the-tube will draw-a constant current from apower supply; and external circuit'parts are eliminated;with+ out sacrifice to fidelity of response. A further object is to provide a tube in. which microphonic troubles. are, to .ta;. large extent, eliminated; and to provide a tubewhich :does not decelerate the..electrons;as they leave the cathode wall. In. the tube herein presented the electron density perunitiareaof the beam cross section remains constant unbecomesgreater. A further. object is to, provide aqtube which can be constructedofyertically alined parts; and which has the ability'to be-usedasa pushpull amplifier with one envelope.

--A further objectis to provide a'tube in which there is no phase shift between; input andoutput. Also in the tube herein presented harmonic and frequency distortion is reduced. a; q

These a d th r obj cts ar ..iia ne b t novel co t on .a d;ar ae emeei 9 1.12am herein-described and illustrated by; the. accomyi r win f rmin Pe t 9 51151 in which:

i Figure 1 isaplanview bra beam amplifier tube embodying'the invention.

lFig. 2is a plan'fviewof mddifid forn'i of the tube. T -1. f ."Fig 3 is a plan viewof another modified 'form ofthe tube. I

Fig. 4 isa plan View of manner modified form ofthetube' l" The tubes herein'presented'are of the same general type as the tube described in"detail'in my application for jpatentf serial No.1 99A99, 'filed June 16, 1949, PatentYNo'. 2,569;971','is'sued October 2, 1951.v Referring-to'the drawing, in Fig. 1 shown a forniof tubehaving an envelope l, in which is mounted a cathode 2 having a coated. surface ofan oxidefl which emits electrons when properly heated.

The emitted electrons are. repelled by a charge at or near cathodepotential'appliedto a focusing structure 4; comprising substantially, a cylinder with an opening "5 for the-passage of" electrons towards accelerating structure including o a plate 6 located to OIIQSidE as"-'s hown'in }Figl -15 --The eiTective width of the opening 5 can be controlled byvarying the voltage tothe focusin'g'structure. Beyond the opening}, 'the plate-fifwhich ispositively charged; causes-electrons emitted from the-cathode 2 to accelerate throughthe opening 5;

the electrons pass through the opening 5 they have a high linear .velocity; "a'nd-the various electron paths 'approachcollimation in a vertical plane, considering that thecathode is vertically aglined; i1): 1 p I J l r i Inthis manner-'a -beam-is set up; vThe. focusing structure allows x the elections tos-Finove l'only throughthe'opening 5, caiisingithezformation of a beam. in the horizontaliplane and the accelerating'structurecauses-the electrons to approach collimation in a verticalplane, with resultant equal. electron density along the vertical axis. 1' i 1 E1ectrons .movingioutward fromtthe opening 5 are. attracted by :a positive deflection plate, I, which is curved inwardly towards .ftheuelect'ron beam. That is, the center ofcurvatureofthe positive deflection plate. is on- .the-sameside of the plate as the electron beam; =A1negative deflection plate 8 is 'maintainedat gorfbelow, cathode potential and consequently'itwill not be bombarded .by electrons; moving outwardly from theopening 5. Since the electrons cannot bombard the plate 8 they begin tolo sesonie of the applied linear.. velocity. The ieardnsare deflected from plate. '8 and attracted towards plate I, which is in line with a target plate 9 having substantially the same curvature in the same direction as plate 1. Plate 9 also has applied thereto a positive potential and the electrons acquire a high angular velocity, which together with the efiect of the negative deflection plate 8 and the positive potential applied to a target anode l0 cause the curved paths of the electrons to converge and focus on the separator plate. The patho'f the electron beam can obviously be controlled by varying the potentials on the various plates 1, 8 and 9.

It will be seen that the electrostatic field shift is but a small part of the control factor. For that reason this tube is not to be construed as simply an electrostatic deflecting tube. The electrostatic shift is secondary to the lens warp which occurs when deflection plate potential is applied and shifted. Aseparator plate H is operated at a lower potential than the target anode insofar as static potential is concerned and will maintain some, potential diiference even at maximum swings in the voltage applied to either the target anode or target plate. Since it is operated at a lower potential in a field of much higher potential the total amount of beam current bombarding the separator plate at no time very large. This current is normally zero.

When the point of focus is placed upon the separator plate the beam will divide on either side oi the plate an be, flowing equally to the target anode and to thetarget plate.

In Fig. l is shown the, circuit for a zero res sistancel audio amplifier.

In this case the currents, of the positive deflecting plate and target plate are combined by typing the two together. The resultant negative resistance for the combined elementsis quite large and can be balanced with an equal but opposite positive resistance on the target anode.

'With the target anode and target plate currents" equal and opposite and with the tar et plate and target anode resistancesequal in mag nitpde but opposite in polarity the resultant gain, with. ass m fiis ent of n r lo e snrqw in ms is x r m y large in ub resistance-is effectively cancelled out.

2 s h w mqdi i cl form irt e th n whic positive. defl ctin p a eis omi e InF 1. n the. vo taseand. p rapha e; ampl thepotential deflecting plate. and he. misfi 9 5 are sep at l nnectsd he. cuit-1 insi ht shown in Fig. 2; is similar tothe' tubeofiFig. 1, and can be used on both the voltage andzpara; phase, amplifier with slight changes inthe positions of the elements. between the two... In the tubes. the active cathode. is maintained. relatively small and arranged so thatthe beam current will be low without sacrificing electron density. As a voltage amplifier, the target plate resistance can be raised to infinite values if desired, either by slightly changing the position of the potential deflecting plate. I, or by slight changes. in the voltage applied. The resistance of target anode I0 is reduced to low. values by such action.

7 In. Fig. 2 is shown the circuit fora single. end A. F. voltage amplifier.

This circuit employs av model of the tube having a high target plate resistance butwith a correspondingly low'target anode resistanceresultingirom this small; change in structure. Also the total current is restricted, if desired; to very low values.

The target plate resistance being large but with the change in target anode and target plate currents remaining equal due to the control of the negative deflecting plate, the amplification of this tube will be very large with an extremely low distortion. Since the characteristic curve of transconductance is straight over a much larger portion of the tubes curve and since the normal driving or zero signal point is exactly halfway along the curve with equal straightline portions on either side, this tube can be driven, as can all tubes of this type, much'harder without distortion than can the ordinary tube.

In Fig. 3, a modified form of tube is shown in which the elements are similar to the tube of Fig. l with the exception that the separator plate H of Fig. 1 is omitted and the target plate 18 and the target anode 29 are substantially semi-cylindrical in shape opening towards the cathode, forming Faraday boxes. This type of tube can be used for power amplification and can be made with low plate resistors.

In Fig. 3 is shown the circuit for a push-pull audio power amplifier.

The tube in this case has a high total current (produced by the increased cathode length) and a low plate resistance (produced by the Faraday box construction of the target plate andtarget anode) With an audio input signal on the negative deflecting plate producing signal voltage changes which will changethe relative negative deflecting plate to cathode voltage theelectron beam will be alternately swung from thetarget anode to the target'plate and back as the signal voltagevaries. Dueto the low internal resistance in the tube the response of this circuit to mechanical inertia in the. speaker or to changing impedanceload in the secondary will be very good, approaching V for very high currents. "Ihis tube can be used with all-the elementsof the tube section to the left operatingin parallel with, the same elements on the'right as shown by the dotted lines... In this case'very high currents with maximum use of the, cathode heating power would be produced. This tubecan also be so connected as to be used as a two stage amplifier in much the same. way as thegpresent day twin triode' is; operated. The cathode is increased in length as are all of; the tube elements, to provide a .m11.ch hi her beam current without vastly increasing the, electron density.

In Fig. 4 is shown the circuitiora cascade audio power amplifier.

The use of a double section tube increases the efficiency of the tubefsoperation by liberating electrons from both sides of the cathode and thus for the-same, or nearly" the same, cathode heating power, double.v the beam. current. is: produced. One of the deficiencies of this type of tube'is the relatively low beam current developed from the cathode heating power. By reducing theactive cathode area and by other means single section cathode eifi'ciencymay be-increased but it cannot approach theemciency of the double element section.

In the cascade audio-frequency power amplifier the two sections of; the beam are used incascade in the same manner as individual sections would be used. In the cascade R. F. poweramplifier the same basic circuit is used. In thev parallel push-pull A. F. power amplifier the elements are simply connected in parallel to develop a larger plate current than could be developed in the single section. The output is taken in pushpull while the input is driving the individual sections in parallel.

From the above description it will'be seen that there has been provided a beamamplifier tube ofsimple, structure, easy to manufacture and control, andwhich is arranged to provide abeam of L'COIlStGJlt intensity, that is, the current drawn from the cathode is, or nearly is, a constant, which. is not true of tubes heretofore provided. The description is to be considered as illustrative and not limitative of the invention of .which modifications can be made without departing from the spirit and scope of the invention. as set forth in the appended claims. j

'I claim: 1. Anelectron discharge device comprising'an envelope,.an electron emittingvcathode mounted insaid envelope, a beamgfocusing means partially surrounding the electron emitting cathode, separate accelerating electrodes disposed to either side of the opening in the beam focusing means, a curved control electrode disposed with its extreme end obstructing the electron beam path as produced by said beam focusing means and said accelerating means, a target plate, and a target anode disposed to the end of said control electrode and near the end of said accelerating electrode opposite the control electrode with said accelerating electrode and said electron beam converging toward one another.

2. An electron discharge device comprising a cathode, beam forming means with an opening, for the passage of electrons formed into a beam, separate accelerating means disposed to either side of said opening with one of said accelerating means curved in its outer extremity to intercept electrons in said beam, a control electrode disposed parallel to said beam near said 'accelerating means with said control electrode curved into the path of said beam at the outer extremity of said control electrode, and a target anode positioned between the outer extremities of said curved accelerating electrode and said control electrode.

3. An electron discharge device comprising a cathode, a beam forming means partially surrounding said cathode and directing electrons into beam paths, accelerating means disposed beyond said beam forming means and further disposed with such relation to said cathode and said beam forming means as to prevent electrons in said beam paths striking said accelerating means, a curved control electrode so disposed as to curve into said beam paths, a curved target anode disposed near the end of said control electrode, and a curved target plate disposed near the side of said target anode with the center of radius of the curves, said target plate and said target anode disposed towards the cathode.

4. An electron discharge device of the amplifying type comprising a cathode, beam forming members disposed at'either side of said cathode, accelerating members disposed beyond said beam forming members from said cathode, curved deflection control plates with one positioned on either side of said cathode beyond said accelerating members and curved into the electron beam paths as projected from said accelerating members, a curved target anode positioned near the extreme end of said curved control plateon either side of said cathode, and a curvedtarget plate positioned on either side ofsaidcathode with the centers of radius of said curve, in said target anode and said target plate disposed to-,- wards Isaidcathode."

5- An electron discharge d vice of -thebeam amplifying type comprising a ;cathode,; beam formingmeanspartially surrounding said cathode, accelerating means disposed to either; side of the opening in said beam forming means with one accelerating member disposedinto a curve along the path, of saidelectron beam with the center of radius of said. curve disposed towards said electron beam, acurvedcontrol electrode disposed to the other side of said electron beam with the center of radius of said curve disposed towards said electron beam, a curved target plate disposed near; the end of said curved control electrode .with the center of radius of saidcurve disposed towards the cathode, .a substantially circular target anode. disposed near the ,end of said control electrode, and a flat separator'plate disposed between said target anode and said target. plate. a

6 An electron discharge device comprising a cathode, beam forming means partially surrounding said cathode, accelerating means disposed to either side of the opening in said beam forming means and further disposed as to be shielded from direct electron bombardment from said cathode, a curved control electrode disposed near one accelerating member and further disposed to curve into the path of said electron beam as projected by said accelerating ,means, a target anode disposed near the end of said control electrode, and a target plate disposed between said target anode and said accelerating means opposite said control electrode.

7. An electron discharge device comprising a cathode, a beam forming means partially surrounding said cathode, a fiat accelerating member on one side of the opening in said beam forming means with the major dimension of said accelerating member substantially perpendicular to the electron beam formed by said beam forming means with said accelerating member further disposed to be shielded by said beam forming means from direct bombardment from said cathode, an accelerating member disposed to the other side of the opening in said beam forming means and shielded by saidbeam forming means from' direct bombardment from said electron beam with said accelerating means further disposed to be farthest away from the electron beam path at the center of width of said accelerating means, a curved control electrode disposed beyond said fiat accelerating'member from said cathode with said control electrode curving into said electron beam as the distance from said cathode is increased, and a target anode disposed near the extreme end of said control electrode as seen from said cathode.

8. The structure set forth in claim 7 in which the target anode is a curved member with the center of radius of said curve disposed toward said cathode.

9. The structure set forth in claim 7 in which the target anode is a substantially circular rod and a separator plate is disposed to the side of said target anode opposite from the side of said target anode disposed toward said control electrode.

10. An electron discharge device comprising a cathode, beam forming means partially surrounding said cathode,-a firs fi aecele'ratingmember: disposed -to one sidebf the'opening in said beam-forming-means anci further disposed to be shielded by said beam forming mea ns from direct bombardment from said cathode, apsecond accelerating member disposed to thee-opposite .side of said-opening in s aid beam forming 'means and further disposed to; be shielded by said beam forming-means r frbn'ri directbombardment from said cathode'kvitii f-saidi seoondacceleratinamembewfurthei disposed-"60 be farthesb from sai'd' election beamt at the center of width of i said accelerating member,- a,curved control electrode disposed beyond 'sdi-d firs'baecelerating:member 'as seem from said cathode: and-further disposed=to curve into the-- path of said electron beam assaid v beam progresses away from said cathode,. a =tairgetanode formed ofla curved member withihe centei o'f recliusof said :c'urv'e disposed "towards said icathode -with said marget anode disposednearr the' end of said control electrode, and atargetiplate forme'd o't -'a substantially curveddmember with :the:eenter 1 or radius. .of said :curve disposed towardssaidieath ode with said target plate further dispdsedi-bes tween: Said target, anode and saidsecnd am celerating' mans.- a 17;.-

- Q MAN Z; 'BALLANTSDZNE; v y REFERENCES mime? 1 j The following references t'r'e off r' oi 'd the meoftms-patent: ig N TED S im -FAfiN Number Date 2,107,520: Feb 854938 2,144,085 --J3 n'3 1 75 1939 2,203,221 J11I1'8 491940 $219,102 Oct 22, 4940 2,225,325 Deb; 17-}1940 2,228;980I steimel et al. Jan 14,1941 2,236,860 Van'Overbeek Apr; --1',= 1941 2,254,095 Thompson; 11g; 2621941 2,254,096 Thompson v--A"t'1g'. 26", "1941 2,280,228 G1over' Apr} 21, 1942 2,305,617 Hansen Dem-2211942 2,390,250 Hansell --DG.'-4'}- 1945 2,539,250 Hosemanh "Jan-23, 1951 2,569,971 Ballantyne O'ct. 2 1951 

